This invention relates to magnetic tape loading mechanism and method for withdrawing a magnetic tape from a cassette which takes in rolled tape, and wind the resultant tape around a magnetic head-carrying rotary drum. The products to which the present invention applies include, for example, a video tape player (VTP), a video tape recorder (VTR) and a digital audio tape recorder.
There is a known VTR in which a cylinder is provided into the front opening of a tape cassette so that the cylinder overlaps the tape cassette. For example, Japanese Patent Laid-open No. 171070/1984 discloses this type of VTR.
FIGS. 1 and 2 roughly show the construction of a tape loading mechanism for the conventional VTR disclosed in Japanese Patent Laid-open No. 171070/1984.
FIG. 1 shows a non-loaded state, in which a tape has not yet been loaded on a cylinder, of the on which the tape loading has been completed and a cassette 4 are arranged in an overlapping manner, of the same tape loading mechanism.
The conventional tape loading mechanism shown in FIGS. 1 and 2 is provided with a first chassis 1, a second chassis 2, a cylinder 3, and tape withdrawing members (which will hereinafter be referred to as tape guides) 6a, 6b. The tape 5 is held in the cassette 4. The cassette 4 is provided with a front opening 4a.
In order to shift the unloading mode of FIG. 1 to the loading mode of FIG. 2 (this operation will hereinafter be referred to as a loading operation), the tape 5 is withdrawn from the front opening 4a of the cassette 4 by the two tape withdrawing guides 6a, 6b toward both the left and right sides of the cylinder 3 and wound around the cylinder 3 as much as a predetermined angle (this operation will hereinafter be referred to as a tape loading operation). During this time, the second chassis 2 on which the cassette 4 is placed slides linearly along grooves (not shown) in the side portions of the chassis 2 over the upper surface of the first chassis 1 on which the cylinder 3 is set, so that the cassette 4 is disposed so as to overlap the cylinder 3 at the opening 4a of the cassette 4.
The specification of Japanese Patent Laid-open No. 171070/1984 discloses an embodiment in which the second chassis starts sliding simultaneously with a tape loading operation, and an embodiment in which the second chassis starts sliding after the completion of a tape loading operation.
A loading mechanism shown in FIG. 2 is a so-called M-loading type tape loading mechanism in which a tape is wound around a cylinder in the left and right directions thereof.
There are some other loading systems, for example, .tau.- and u-loading systems developed by reducing the height of the tape path and the tape running load in the above M-loading system.
The outline of a tape loading mechanism for the .tau.-loading system is shown in FIG. 3. In the tape loading mechanism for the .tau.-loading system, a tape loading guide 6a hooks a tape 5 and move to a catcher 15a, while a tape loading guide 6b moves after the tape loading guide 6a to a catcher 15b.
The routes of movements of two tape guides 6a, 6b in the M- and .tau.-loading systems will now be compared. When the tape loading is ready to be started, the two tape withdrawing guides 6a, 6b are all held in the front opening 4a of the cassette so that the tape 4 can be withdrawn thereby in both of these loading systems. When a tape loading operation is started, the two tape withdrawing guides 6a, 6b move to right and left, respectively, to load the tape in a laterally divided manner on the cylinder in the M-loading system, so that the tape guides 6a, 6b run out of the opening 4a in the front portion of the cassette speedily. In the .tau.-loading system, the two tape withdrawing guides 6a, 6b move out to the same side of the cylinder, so that, especially the rear tape guide 6b with respect to the tape loading direction necessarily moves within the opening 4a in the front portion of the cassette for a predetermined period of time during the initial part of the tape loading operation.
Therefore, when the second chassis 2 in the .tau.-loading system starts sliding simultaneously with the starting of a tape loading operation in the same manner as in the first embodiment of the invention disclosed in Japanese Patent Laid-open No. 171070/1984, the rear tape guide 6b contacts the side surface 4b of the opening 4a at the front portion of the cassette 4 to obstruct the tape loading operation.
In the case where the second chassis 2 starts sliding after the completion of a tape loading operation, the following problems arise.
(i) A total period of time required for carrying out a tape loading operation becomes equal to the sum of the tape loading time and chassis sliding time, i.e., it becomes longer. PA1 (ii) Since the second chassis 2 starts sliding after a tape loading operation has been completed, it is necessary that the slackening of the loaded tape be prevented. Therefore, the tape must be taken up at the same time that the sliding of the chassis is done.
According to the above-described conventional techniques, the second chassis 2 is slid by driving a rack 2a, which is provided thereon, by a pinion 12 provided on the first chassis 1. However, in this tape loading system, backlash between the rack 2a and pinion 12 and an error of rotation occur. Consequently, the precision of positioning of the second chassis 2 in the sliding direction during a tape unloading operation and at the time of completion of a tape loading operation decreases to a low level. This often causes erroneous operations of a brake and a mode control member (not shown) the operations of which need be transmitted from an operating member on the first chassis to a member to be operated which is provided on the second chassis 2. Namely, the conventional tape loading system has problems with respect to its reliability.
The inventions having relation to the present invention include the inventions disclosed in the following publications.
U.S. Pat. No. 4,611,251, U.S. Pat. No. 748,521, U.S. Pat. No. 4,4,789,912, U.S. patent application Ser. No. 925,908 (filed in November 1986).